1. Field of the Invention
The invention relates to external storage devices with a thin thickness type that are releasably or exchangeably used for storage equipment and devices as an external storage medium.
2. Description of the Related Art
Two types of storage devices (memory elements), which are capable of recording and saving various data, have been utilized, namely, one is incorporated and fixed within storage equipment or devices, and the other is releasably or exchangeably incorporated in the storage equipment or devices. For the latter type, the external storage device, for example, floppy disks can freely be attached or detached by one touch operation. The floppy disks being the storage mediums can separately be used depending on purpose and object. This therefore produces easier data reduction with optional classification, recording, and saving. However, a problem arises in the floppy disks described, where first, the data occasionally disappears when recording or saving the data disadvantageously making the floppy disk less reliable together with its slower access time. Next, when employing the smaller sized floppy disks in response to a miniaturization policy, a storing area of the storage medium is correspondingly smaller to reduce storage capacity, thus giving the adverse effect in realizing the compact size and high capacity therefor. On the other hand, semiconductor memory devices used as an external storage device, such as IC memory cards, can largely solve the problems in the floppy disks such as less reliability on recording and saving the data and the slower access time. In general, the IC memory cards comprise a functional circuit in which circuit components containing the semiconductor memory devices or elements are mounted on substrates, a resin case incorporating therein with the functional circuit as an inside attachment, a cover for covering and sealing an opening surface of the resin case, and external connection terminals such as two piece connectors which are attached on one edge of the resin case and electrically connect the functional circuit and the storage equipment/device.
However, the IC memory cards are assembled with a large amount of components and parts, where a relatively complicated structure is required with limitation to a thickness of the IC memory card, resulting in the difficulty in realizing the compact size. Further, disadvantages arise in practical use because of lower cost performance or production yields during mass production in addition to the less releasability or fluctuated releasability to the storage equipment and device.